FIG. 1 illustrates a block diagram of a prior art front-end circuit for a radiation detector. The circuit includes a low-noise charge amplifier 102, a filter 104, and a peak detector 106. A charge signal Q from a sensor of the radiation detector is amplified by the charge amplifier 102 and filtered by the filter 104, yielding a voltage pulse v(t) with an amplitude proportional to the charge Q. The voltage pulse is processed by the peak detector 106 which yields a constant voltage vp(t) equal to the peak pulse amplitude U. The constant voltage is then processed by further voltage-input processing electronics 108, such as a voltage-input Analog-to-Digital converter.
The peak detector 106 in FIG. 1 is only capable of operating with voltage-input processing electronics 108. If a current-input processing device or circuit is required, such as a current-input Analog-to-Digital converter, a stage which converts the voltage vp(t) into a current is required. Such an additional stage utilizes additional power.
Moreover, in order to maximize the dynamic range of the analog front-end circuit, the peak detector 106 must be able to operate rail-to-rail, i.e. it must be able to process voltages that swing from the minimum (typically ground) supply voltage to the maximum supply voltage, while preserving the required detection precision. Such a rail-to-rail circuit can be affected by non-linear errors due to voltage offsets at the complementary differential input stages, resulting in low-precision peak detection.
In U.S. Pat. No. 6,512,399, which is herein incorporated by reference in its entirety as if fully set forth in this disclosure, G. De Geronimo et al. disclosed a high-precision peak detector capable of operating rail-to-rail by using an offset-cancellation method. However, the disclosed circuit operates with voltage-input processing electronics, and one or more additional stages which precisely convert the voltage vp(t) into a current may be desired. Such additional stage(s), along with utilizing additional power, may be desired to operate with rail-to-rail input voltages but without being affected by non-linear errors due to voltage offsets at the complementary differential input stages.
Therefore, there is a need to develop a peak detector capable of operating with rail-to-rail voltage inputs and providing an output current for operation with current-input processing electronics. There is also a need for a peak detector that is capable of providing high degree of precision peak detection.